Helix Nebula

The Helix Nebula ( NGC 7293 also called ) is a planetary nebula in the constellation Aquarius likes having a brightness of 6.30 and an apparent diameter of 16.0 '× 28.0 '. It was discovered in 1824 by the German astronomer Karl Ludwig Harding.

The Helix nebula is at a distance of about 650 light-years of the next planetary nebula and thus with the projected largest diameter (about half the size of the projected moon). Therefore, details of the gas structure can be resolved into its sheath.

With the Hubble Space Telescope in 1996 it was even the first time possible to include nodes in the envelope that were previously unknown and allowed new conclusions about the formation of planetary nebulae. But they also raised new questions. So it is not clear whether the node nuclei formed during the ejection of the envelope or whether they originate from activity of the star before ejection. Also, it is debatable whether the nodes are hydrodynamic structures (that is generated by instabilities ) or whether they are created by photoionization of the gas by the white dwarf in the center.

UV absorption by GALEX

Infrared image from the Spitzer Space Telescope: blue 3.6-4.5 microns; green 5.8 to 8 microns; red 24 microns